This invention relates to a process for producing copper base alloys and terminals that are made of those copper base alloys for use in automobiles and other applications.
Copper base alloys for use in terminals in automobiles and other applications have conventionally been selected from among brass, phosphor bronze and other copper base alloys such as Cu-Sn-Fe-P systems.
In response to the recent advances in electronics technology, connector terminals for use in automobiles and other applications have increasingly been required to satisfy the need for higher packing density, smaller scale, lighter weight and higher reliability. On the other hand, the constant improvement in the engine performance has led to a higher temperature in the engine room. Under these circumstances, there has arisen the need that the copper base alloys for terminals that are used as conductive materials on the engine should have even higher reliability and heat resistance. However, brass that has heretofore been used as an inexpensive copper base alloy for terminals has low electrical conductivity (to take C2600 as an example, its electrical conductivity is 27% IACS); it also has problems with corrosion resistance and stress relaxation characteristics. Further, phosphor bronze has high strength but its electrical conductivity (hereunder simply referred to as "conductivity") is also low (to take C5210 as an example, its conductivity is ca. 12% IACS); in addition, it has problems with stress relaxation characteristic and from an economic viewpoint (high price). Cu-Sn-Fe-P alloys have been developed with a view to solving those problems of brass and phosphor bronze. For example, Cu-2.0Sn-0.1Fe-0.03P has a conductivity of 35% IACS and is superior in strength; however, its stress relaxation characteristic has not been completely satisfactory in view of its use as an alloy for terminals.
For manufacturing highly reliable automotive terminals, it is necessary to use copper base alloys that are superior in strength spring limits and conductivity and that will cause neither stress relaxation nor corrosion after prolonged use. However, none of the conventional copper base alloys, i.e., brass, phosphor bronze and Cu-Sn-Fe-P alloys, have satisfied those requirements.
A further problem is that the terminals manufactured from the aforementioned copper base alloys reflect the characteristics of those alloys in a straightforward manner. The terminals using brass, phosphor bronze or Cu-Sn-Fe-P alloys do not satisfy the requirements for high conductivity and good stress relaxation characteristics simultaneously, so they will generate heat by themselves, potentially causing various problems including oxidation, plate separation, stress relaxation, circuit voltage drop, and the softening or deformation of the housing.